This invention is directed generally to control members such as knobs, and more particularly to a positive-positioning knob assembly which may be used on any device having a rotatable shaft which requires positive incremental positioning or "detenting".
Many rotating control devices such as potentiometers, rotary switches, or the like require positive detenting or incremental positioning to achieve and maintain separately definable positions thereof. For example, such positions might correspond with preselected incremental values of resistance of a potentiometer, and be defined by a knob or dial member having a pointer or other indicia alignable with incrementally located indicia on a facing panel or the like. In order to achieve such incremental positioning or detenting action, various mechanical releasable interlocking or detenting arrangements may be utilized. Many such arrangements utilize simple cam arrangements wherein a cam member rides over a series of facing cam members positioned incrementally to approximate the desired incremental positioning of the knob or other control member. Such arrangements may require only an increased rotational force or torque applied to the knob or control member to achieve the incremental movement. However, many applications require either a more accurately defined, or more finely resolved incremental positioning capability than possible with a simple cam arrangement. Other installations may additionally require that the knob or other control member be more positively locked against movement upon reaching or achieving a desired position or setting, such that some additional locking or unlocking manipulation, other than mere increased rotational force or torque is required to release and reposition the knob or other member.
The present invention proposes a relatively simple and inexpensive positive positioning and incrementally positionable, releaseably locking knob assembly which achieves the foregoing objects. That is, the knob assembly of the invention permits incremental rotation of a control shaft, or other member over a broad range of coarse to fine resolutions of equal incremental angular positions out of a 360 degree or any other desired total angular range of rotation. Moreover, the knob assembly of the invention provides a positive locking feature which requires positive manipulation of the knob in a direction other than the rotational direction for release thereof to achieve repositioning of the same. This locking feature automatically takes effect when the knob is released following revolution thereof to lock the same substantially in the last rotational or angular position achieved during revolution.